1. Field of the Invention
The instant invention relates to a device for the introduction of a gas in a finely divided form into a liquid medium, and more particularly to a rotor for the introduction of air in a finely divided form in an flotation device.
2. The Prior Art
Flotation is a well-known technique used to separate one or more valuable constituents from unwanted constituents. A typical field of use for flotation is in the enrichment of ores in which finely divided air is introduced into an aquous suspension of finely divided ore and water. The finely divided air bubbles will adhere to the metal values of the ore and carry the same to the surface of the basin in which the flotation is carried out. The metal values and the air bubbles will usually form a foam on the surface which can be removed by skimming.
In order to improve the selectivity and effectiveness of the flotation process certain adjuvants such as surface active agents are added to the suspension. These agents bring about a better adhesion between the metal values and the air bubbles.
A general account of the flotation process is inter alia found in Kirk-Othmer, "Encyclopedia of Chemical Technology", second edition, volume 9, pages 380-398.
The air can be introduced in the suspension of the finely divided material in different ways; for instance, water saturated with air under pressure can be introduced to the suspension and, as a consequence of the pressure release, the absorbed air will be liberated in the form of finely divided bubbles.
However, the most common manner in which the air is finely divided is by means of mechanical agitation, for instance by means of a rotor which more or less "whips" added air into the suspension.
Such mechanical devices are inter alia described in Norwegian Pat. No. 116,156, U.S. Pat. Nos. 2,609,097 3,070,229, 3,327,851, 3,393,802, 3,393,803, 3,409,130, 3,437,203, 3,485,484 and 3,752,313 and German DOS No. 26.59.230.
For flotation purposes it is desirable for the added air to exhibit the greatest possible surface area with respect to the added volume of air, that is, the air should be introduced in the form of very finely divided and minute bubbles.
In U.S. Pat. No. 2,609,097 a rotor is described into which air is introduced centrally via a supply pipe and is radially distributed to the suspension via a number of conduits leading to the periphery of the rotor, these conduits opening into a groove, one side of which is formed in such a manner that the air, during the rotation of the rotor, is forced into the adjacent suspension.
U.S. Pat. No. 3,485,484 discloses for instance a rotor in which the air is centrally supplied and led out through conduits in the wings of the rotor and thus forced into the surrounding suspension.